This occurred during my LabView Core 1 Training, during one of the lessons, using Google Chrome.
It normally happens 20 to 30 minutes after I have been on the website. It has happened on FireFox too.
There could be several reasons. But from my experience, I have had similar situation on my windows PC. But everything worked fine on MAC OS running "Safari" web browser.
If you do not have MAC OS try downloading Safari for windows. It may help.
Looks like trying to get Safari for Windows is now an outdated solution.
According to their website:
Apple no longer offers Safari updates for Windows. Safari 5.1.7 for Windows was the last version made for Windows, and it is now outdated.